Write a program in C# Sharp to find sum of right diagonals of a matrix ?

using System;  
public class Exercise23  
{  
    public static void Main()
   {
     int i,j,sum=0,n;
   	 int[,] arr1 = new int[50,50];
       Console.Write("\n\nFind sum of right diagonals of a matrix :\n");
       Console.Write("---------------------------------------\n");	 
	 Console.Write("Input the size of the square matrix : ");
	 n=Convert.ToInt32(Console.ReadLine());
	 Console.Write("Input elements in the first matrix :\n");
       for(i=0;i<n;i++)
        {
            for(j=0;j<n;j++)
            {
	           Console.Write("element - [{0}],[{1}] : ",i,j);
			   arr1[i,j]=Convert.ToInt32(Console.ReadLine());
			   if (i==j) sum= sum+arr1[i,j];
            }
        }  
	 Console.Write("The matrix is :\n");
	 for(i=0;i<n;i++)
	 {
	   for(j=0;j<n ;j++)
	     Console.Write("{0} ",arr1[i,j]);
	    Console.Write("\n");
	 }
       Console.Write("Addition of the right Diagonal elements is :{0}\n",sum);
	   }
    }